1. Field Of The Invention
The present invention relates generally to scuba diving equipment and more specifically to an improved second stage regulator having a balanced linear flow demand valve with a pneumatically activated anti-set poppet seat and inhalation resistance control adjustment knob.
2. Prior Art
Almost all regulators available today use a soft elastomeric seat inside the second stage demand valve mechanism to seal airflow between breathing cycles. However, when the regulator is unpressurized, such as during storage, the rubber seat sits spring loaded against a sharp edge orifice. Over time, the sharp edge orifice penetrates deeply into the rubber seat, causing the second stage regulator to go out of adjustment, leak air and degrade performance. In addition, in conventional second stage scuba diving regulators, the demand valve mechanism spring load is set at the factory and cannot be varied in the field during use. Consequently, the diver has little if any control over the cracking effort required, that is the effort required to open the demand valve mechanism during each breathing cycle. Normally, the spring load is set at a level which facilitates a normal cracking effort within a limited range of maximum tank pressure variation. However, it would be advantageous if the diver were given some control over the spring load to reduce the cracking effort at low tank pressure or during emergency or high demand conditions, such as at significant depths or for example, when two divers must use the same regulator to breathe.
Thus, there is a need in the scuba diving industry for an improved second stage regulator which provides for spring relaxation as an anti-set feature during non-use of the regulator and which provides the diver with a significant degree of spring load control to modify the cracking effort, particularly at extreme conditions.
A search of the prior art has revealed the following nineteen patents which are deemed to be relevant to the present invention in varying degrees:
______________________________________ 3,362,429 Volsk 4,094,314 Le Cornec 4,159,717 Cossey 4,226,257 Trinkwalder 4,796,618 Garraffa 4,834,086 Garofalo 4,889,115 Bozano 4,971,108 Gottlieb 5,035,238 Christianson 5,092,325 Ainscough 5,222,490 Pomerantz et al 5,233,976 Ferguson 5,245,997 Bartos 5,251,618 Christianson 5,259,374 Miller et al 5,259,375 Schuler 5,265,596 Sauze 5,343,858 Winefordner et al RE 31,932 Christianson ______________________________________
U.S. Pat. No. 4,834,086 to Garofalo is directed to a second stage regulator for an underwater air breathing apparatus with a floating piston that opens the second stage valve during periods of non-use to prevent distortion of the valve seat and the resultant alteration of calibration. When compressed air is applied to the input fitting 7 of valve 4, a valve seat mounting member 8, a floating piston, is forced by the input air against biasing spring 608 into engagement with the bottom of chamber 204 and seat 508 mounted on the floating piston in gauge valve 3. Breathing by the user opens valve 3 through the action of monostat diaphragm 12 and lever 2. The air flow through valve 4 results in a pressure drop upstream of the floating piston, resulting in spring 608 moving the piston back away from valve 3 increasing the air flow to the user at parity with the inhalation effort.
U.S. Pat. No. 4,094,314 to Le Cornec is directed to a second stage pressure regulator that has a nozzle that is held in operating position by the compressed inlet air and when not in use, the nozzle is only lightly held against the sealing pellet so as to cause no irreversible deformation and maladjustment of the pressure regulator. An intermediate body member 4 holds nozzle 5 that is held lightly by spring 15 against the seat 5a of the valve member 5. Pressurized air from the first stage regulator applied to the inlet 1 forces the nozzle against the valve seat for normal operation. The valve biased closed by spring 9 is operated by membrane 19 through lever 11.
U.S. Pat. No. 4,159,717 to Cossey is directed to an anti-set protector for second stage scuba regulators. A removable spacer 52 is provided to be interposed between the cover 50 and flexible diaphragm 42 during storage of the regulator. The spacer holds the valve assembly 20 open so that the closure 26 does not take on a compressive set with the resulting loss of sealing ability.
U.S. Pat. No. 5,222,490 to Pomerantz et al is directed to a second stage demand breathing regulator that provides for selective adjustment by the user. The regulator 10 mounted on mouthpiece tube 12, receives pressurized air into conduit 14. Diaphragm 18 deflects responding to changes in air pressure and opens valve 32 through lever 28. Valve seat 36 and retainer 37 are formed of metal so as to withstand the inlet pressure without deforming. Knob 52 is provided for positioning spring retainer 46 to and fro so as to adjust the bias on the pressure regulating spring 40 for a user selected limited adjustment. During assembly, the valve seat 36 is adjusted by means of the relatively fine screw threads of retainer 37.
U.S. Pat. No. 5,035,238 to Christianson is directed to a second stage regulator for scuba that incorporates a semi-balanced valve mechanism that includes an external adjustment knob for the diver to change the regulator's sensitivity to conserve gas. The second stage regulator 14 with outer case 15, incorporates a diaphragm 17, exhaust valve 21, purge button 22, whisker lever 25 and valve mechanism 26. External adjusting knob 34 provided on valve mechanism 26 has fine threads 35 to adjust the bias on pressure regulating spring 54 and thereby the force applied to the sealing seat 44 against edge 40. The diver can adjust the knob to change the regulator's inhalation sensitivity during special circumstances.
U.S. Pat. No. 5,259,375 to Schuler is directed to a second stage scuba regulator with a diver/user air volume control adjustment. The regulator 10, with a balanced piston breathing apparatus 26, operated by a lever 28 and diaphragm 32, has an air volume control 100 that is independent of the selected resistance. Air volume control 100 has knob 110 provided to screw in stem 102 to vary the occlusion of discharge opening 72, thereby varying the volume of air supplied independent of the selected resistance.
U.S. Pat. No. Re. 31,932 to Christianson is directed to a second stage demand regulator with a user adjustable aspiration control and having a diaphragm that flattens against a platform so as to exhibit a varying effective area resulting in stable operation. The regulator 10 with flow control valve 19 and diaphragm assembly 22 has a rotatable cap 60 that changes the location of aspiration opening 57', thereby adjusting the amount of aspiration provided by the regulator.
U.S. Pat. No. 4,971,108 to Gottlieb is directed to a compact second stage inhalation responsive regulator with a user adjustable inhalation force control. The generally tubular regulator has a cylindrical diaphragm end cage that operates inlet air valve 44 through center post 52. An alternate embodiment, shown in FIG. 9 has an adjusting screw 72 that supports and biases valve spring 50. Changing the bias on the valve spring adjusts the amount of inhalation force necessary to open the valve. From the aforementioned prior art description it will be seen that there is apparently no known prior art which provides an anti-set spring relaxation feature and a spring load control feature in a second stage scuba diving regulator. There is therefore a continuing need for an improved second stage scuba diving regulator of the type having a balanced linear flow demand valve but with a pneumatically activated anti-set poppet seat and an inhalation resistance control adjustment knob.